It is desirable for medical devices that are inserted into the body to have a lubricated or lubricious outer surface to facilitate insertion into and/or removal from the body. Such devices may include, for example, urinary catheters, endoscopes, cardiovascular catheters, syringes, vascular stents, etc. Such medical devices may have a lubricant gel placed on the outer surface of the device or may have a hydrophilic coating or layer disposed on the outer surface of the device. Hydrophilic coatings are becoming the preferred method of providing a lubricious surface because of their high lubricity and ease of use. Hydrophilic coatings become slippery or lubricous when wetted with a wetting fluid, such as saline or water. The wetted lubricous hydrophilic coating eases insertion and removal of the device, minimizes soft tissue damage and reduces overall discomfort during use of the medical device.
When a medical device having a hydrophilic coating is used, the hydrophilic coating is typically wetted for a certain period of time prior to use to activate the hydrophilic coating. For example, the user may immerse or otherwise contact the hydrophilic coating with a wetting fluid to wet or activate the coating. In some instances, the medical device is packaged in a packaging that includes liquid or vapor water within the package that hydrates the coating while the device is in the package so that the device is ready to use right out of the package.
Hydrophilic coatings are oftentimes applied to the surfaces of medical devices by a dip coating process that includes dipping the medical device into a base coat composition which typically includes a solvent, one or more polymers and additives and/or agents. The base coat composition is then cured to form a base coat layer. The medical device is then dipped into a top coat composition to apply the top coat composition over the base coat layer. The top coat composition oftentimes includes a solvent, one or more hydrophilic polymers, and other polymers, additives and/or agents. The top coat composition is then cured to form the hydrophilic coating, which becomes lubricious when wetted.
It is well-known that there are challenges in sterilizing and storing hydrophilic coatings in a “wet” state. For example, it is known that most hydrophilic coatings lose their water retention, have reduced attachment to the medical device and/or that the coefficient of friction increases when the coating is stored in water for an extended period of time and/or after being irradiation sterilized.